The present invention relates to a cylindric drum provided at its circumferential edge with a number of recesses that each are adapted for accommodating a replaceable grinding element including a retainer means in which is mounted a sandpaper, support brushes and/or retainer brushes the recesses in the cylindric drum are made with side walls, that the retainer means are made with corresponding outer side walls and that by wedge action between the side walls of the recesses and the outer side walls of the retainer means a squeezing force on the side walls of the retainer means directed in the circumferential direction arises during use.
By surface treatment, as e.g. grinding or polishing of diverse elements, grinding and polishing tools are used which are designed with a cylindric drum in which is mounted grinding elements that include sandpaper, support brushes and/or retainer brushes.
Typically, these grinding elements are made in a plastic material in which sandpaper and brushes are often moulded. Experience shows that sandpaper and support brushes/retainer brushes are not worn with the same rate. This means waste of material as it is necessary to discard the entire grinding element, even though it is typically only the sandpaper which is worn out.
Since a circumferential edge of a cylindric drum as an average is provided with between 30 and 60 grinding elements with sandpaper and brushes that by industrial use of the grinding or polishing tool are to be replaced regularly, the amount of grinding elements discarded constitutes a problem.
Furthermore, the shape of the element that is desired ground and the control of the cylindric drum during grinding will imply uneven wear of the sandpaper on the cylindric drum so that some of the mounted grinding elements are to be replaced more often.
Different types of cylindric drums exist by which this problem is attempted solved by mounting grinding elements that may be dismounted, after which it is possible to replace sandpaper and/or brushes.
The disadvantage of the type of cylindric drums in which the grinding element is mounted replaceable in rails mounted on the circumferential edge of the cylindric drum is that the rails may damage the surface of an element desired to be ground, if the rails accidentally come into contact with the surface.
The disadvantage of the type of cylindric drums where sections of the grinding element is mounted in recesses and the fastening of the grinding paper to the block/moulding occurs outside the circumferential edge of the cylindric drum is that there is an increased risk of the fastening area of the grinding paper is subjected to unnecessary wear, and thereby the sandpaper is more easily struck/tom off the grinding element.
Common to both the above types is that for fastening both the grinding element to the cylindric drum and the sandpaper to the grinding element as well as securing sandpaper and/or brushes for the grinding element there is used e.g. glue, screws or the like mechanical parts, making difficult dismounting of the grinding element from the cylindric drum and the subsequent replacement of either sandpaper or brushes.